An American scientist has sparked a trans-Atlantic tempest in a teapot by offering Britain advice on its favorite hot beverage.

Bryn Mawr College chemistry professor Michelle Francl says one of the keys to a perfect cup of tea is a pinch of salt. The tip is included in Francl鈥檚 book 鈥淪teeped: The Chemistry of Tea,鈥� published Wednesday by the Royal Society of Chemistry.

Not since the Boston Tea Party has mixing tea with salt water roiled the Anglo-American relationship so much.

The salt suggestion drew howls of outrage from tea lovers in Britain, where popular stereotype sees Americans as coffee-swilling boors who make tea, if at all, in the microwave.

鈥淒on鈥檛 even say the word 鈥瞫alt鈥� to us鈥︹�� the etiquette guide Debrett鈥檚 wrote on X, formerly known as Twitter.

The U.S. Embassy in London intervened in the brewing storm with a social media post reassuring 鈥渢he good people of the U.K. that the unthinkable notion of adding salt to Britain鈥檚 national drink is not official United States policy.鈥�

鈥淟et us unite in our steeped solidarity and show the world that when it comes to tea, we stand as one,鈥� said the tongue-in-cheek post. 鈥淭he U.S. Embassy will continue to make tea in the proper way - by microwaving it.鈥�

The embassy later clarified that its statement was 鈥渁 lighthearted play on our shared cultural connections鈥� rather than an official press release.

鈥淪teeped,鈥� in contrast, is no joke. The product of three years鈥� research and experimentation, the book explores the more than 100 chemical compounds found in tea and 鈥減uts the chemistry to use with advice on how to brew a better cup,鈥� its publisher says.

Francl said adding a small amount of salt 鈥� not enough to taste 鈥� makes tea seem less bitter because 鈥渢he sodium ions in salt block the bitter receptors in our mouths.鈥�

She also advocates making tea in a pre-warmed pot, agitating the bag briefly but vigorously and serving in a short, stout mug to preserve the heat. And she says milk should be added to the cup after the tea, not before 鈥� another issue that often divides tea lovers.

Francl has been surprised by the level of reaction to her book in Britain.

鈥淚 kind of understood that there would hopefully be a lot of interest,鈥� she told The Associated Press. 鈥淚 didn鈥檛 know we鈥檇 wade into a diplomatic conversation with the U.S. Embassy.鈥�

It has made her ponder the ocean-wide coffee-tea divide that separates the U.S. and Britain.

鈥淚 wonder if we鈥檙e just a more caffeinated society 鈥� coffee is higher in caffeine,鈥� she said. 鈥淥r maybe we鈥檙e just trying to rebel against our parent country.鈥�

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